1. Field of the Invention
The present invention relates to a method for transmitting a control signal, which has two-condition capability, between assemblies which are driven asynchronously relative to one another wherein the transmission has a high degree of security against misinterpretation of the control signal.
2. Description of the Prior Art
Control signals between asynchronously running digital assemblies have exactly one active level (logical 0 or 1). Such control signals can be easily unintentionally activated by errors such as a defective drive or a short. This results in an undesirable error propagation which must be avoided at all times in complex systems such as the switching computer of a telecommunications switching installation.
Since asynchronous assemblies run with different clocks and different phases, a synchronous coding is not possible. In conventional systems, only a static control signal with one active level is used. This can result in the misinterpretation of an apparent control signal, particularly given the failure of the operating voltage of an assembly or the dismantling of the electrical connections of an assembly, such as in the retraction of the assembly from its connecting plug.
It is therefore an object of the present invention to propose a method for forwarding a control signal between asynchronously driven assemblies in which there is a high degree of security against a misinterpretation of the control signal.
Such object is achieved in a method wherein the inventive coding, which is suitable for asynchronous assemblies, avoids the abovementioned error and its propagation and thereby sharply increases the reliability. A realization of the inventive method includes an extensive insensitivity to jitter in the sequence of the change of condition of the coding signal and does not require any additional hardware outlay compared to the conventional solution.
Additional features and advantages of the present invention are described in, and will be apparent from, the Detailed Description of the Preferred Embodiments and the Drawings.